JP2003248091A - Radiation image conversion panel and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiation image conversion panel and its production method providing sharpness to the image. <P>SOLUTION: The radiation image conversion panel consists of stimulable phosphor sheet having at least a support body and a stimulable phosphor layer. The support body is a transparent support of thickness of 100 μm or larger and has an exciting light absorbing layer on the surface side opposite to the stimulable phosphor layer surface. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation image conversion panel using a stimulable phosphor and a manufacturing method thereof, and more particularly to a radiation image conversion panel excellent in sharpness and a manufacturing method thereof. Is.

[0002]

2. Description of the Related Art Radiation images such as X-ray images are widely used in the fields of disease diagnosis and the like. Conventionally, as a method for obtaining this X-ray image, for example, X-rays that have passed through a subject are irradiated to a phosphor layer (fluorescent screen) to generate visible light, and then this visible light is used for normal photography. The so-called radiographic method is widely used in which a visible silver image is obtained by irradiating a silver halide photographic light-sensitive material (hereinafter, also simply referred to as a light-sensitive material) in the same manner as in the case of taking an image, and then performing a development process.

However, in recent years, a new method of directly taking out an image from a phosphor layer has been proposed instead of an image forming method using a light-sensitive material having a silver halide salt.

As this method, the radiation that has passed through the subject is absorbed by the phosphor, and then the phosphor is excited by, for example, light or thermal energy, and the radiation accumulated by the phosphor is absorbed. There is a method in which energy is emitted as fluorescence and this fluorescence is detected and imaged.

Specifically, for example, US Pat. No. 3,85
A radiation image conversion method using a stimulable phosphor as described in JP-A No. 9,527 and JP-A No. 55-12144 is known. This method uses a radiation image conversion panel containing a stimulable phosphor, and the radiation transmitted through the subject is applied to the stimulable phosphor layer of this radiation image conversion panel to determine the radiation transmission density of each part of the subject. Is accumulated in the stimulable phosphor by time-sequentially exciting the stimulable phosphor with electromagnetic waves (excitation light) such as visible light and infrared rays. Emit radiation energy as stimulated emission,
The signal depending on the intensity of the light is photoelectrically converted to obtain an electric signal, and the electric signal is reproduced as a visible image on a recording material such as a silver halide photographic light-sensitive material or a display device such as a CRT. is there.

According to the above-mentioned method of reproducing a radiographic image, compared with a conventional radiographic method using a combination of a radiographic film and an intensifying screen, the radiographic image has a much smaller exposure dose and is rich in information amount. Has the advantage that

As described above, the stimulable phosphor is a phosphor that exhibits stimulated emission when irradiated with excitation light after being irradiated with radiation, but in practice, excitation with a wavelength in the range of 400 to 900 nm is used. A phosphor that emits stimulated emission in the wavelength range of 300 to 500 nm by light is generally used.

In the radiation image conversion panel using these stimulable phosphors, the radiation energy is released by scanning the excitation light after the radiation image information is stored, so that the radiation image can be stored again after the scanning. It can be used repeatedly. That is, in conventional radiography,
The radiographic film is consumed for each photographing, whereas the radiographic image conversion panel is repeatedly used in this radiographic image conversion method, which is advantageous in terms of resource conservation and economic efficiency.

The superiority or inferiority of the radiation image conversion system using the radiation image conversion panel is greatly influenced by the stimulable luminescence brightness (also referred to as sensitivity) of the panel and the sharpness of the obtained image. However, it is said that the characteristics of the stimulable phosphor used have a great influence. In particular, the reduction in sharpness in the radiation image conversion panel is caused by the excitation light incident from the surface of the panel being diffused and diffused in the stimulable phosphor plate.

The spread of the excitation light in the stimulable phosphor plate is due to diffusion in the protective layer or the stimulable phosphor layer and reflection at the interface between the support and the phosphor layer. Since the excitation light is coherent light with a long wavelength from red to infrared, the amount absorbed is small unless the scattered light or reflected light is positively absorbed.
Propagates to distant places and deteriorates sharpness.

In order to prevent the excitation light from diffusing in the stimulable phosphor layer, for example, the phosphor layer is colored blue. To prevent the excitation light from diffusing in the protective layer, the protective layer is colored blue. A method of coloring the phosphor layer blue, a method of coloring the adhesive layer (undercoat layer) blue, and the like can be considered for preventing excitation light reflection at the interface between the support and the phosphor layer. For these methods, for example,
Japanese Patent Publication No. 59-23400 discloses a method of coloring any of the support, the undercoat layer, the phosphor layer, the intermediate layer and the protective layer of the radiation image conversion panel with a color that absorbs excitation light. Further, Japanese Patent Application Laid-Open No. 60-200200 discloses a method of coloring an adhesive layer between a phosphor layer and a protective layer, but any of these methods absorbs only excitation light and transmits stimulated emission light. For that purpose, the colorant that absorbs the excitation light is limited to the blue color, and it is the current situation that it is not possible to obtain a sufficient effect of absorbing the excitation light. A technique for promptly improving the deterioration of the sharpness due to the spread of the excitation light. Is required to be developed.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object thereof is to provide a radiation image conversion panel which gives an image having excellent sharpness and a method for manufacturing the same. .

[0013]

The above-mentioned object of the present invention can be achieved by the following constitution.

1. In a radiation image conversion panel comprising a stimulable phosphor sheet having at least a support and a stimulable phosphor layer, the support is a transparent support having a thickness of 100 μm or more, and the support is sandwiched between the transparent support and the support. A radiation image conversion panel having an excitation light absorption layer on the surface opposite to the surface of the stimulable phosphor layer.

2. The radiation image conversion panel according to item 1, further comprising a low refractive index layer between the support and the excitation light absorption layer.

3. 3. The radiation image conversion panel according to 1 or 2 above, wherein the haze ratio of the support is 20% or more and the transmittance at the excitation light wavelength is 80% or more.

4. A phosphor sheet having a stimulable phosphor layer on a support, and a phosphor sheet disposed above and below the phosphor sheet, substantially not adhered to the stimulable phosphor layer, and a peripheral edge of the phosphor sheet. In a radiation image conversion panel which is outside the periphery and is provided with a moisture-proof protective film provided so as to cover the entire surface of the phosphor sheet, the support of the phosphor sheet has a transmittance of 80% at the excitation light wavelength. The radiation image conversion panel is characterized in that the resin layer of the moisture-proof protective film on the support surface side contains a coloring agent that absorbs excitation light or has an excitation light absorption layer. .

5. The radiation image conversion panel according to any one of items 1 to 4, wherein the excitation light absorption layer is black.

6. A method for manufacturing a radiation image conversion panel, comprising manufacturing the radiation image conversion panel according to any one of items 1 to 5.

As described above, the reduction in the sharpness of the radiation image conversion panel is caused mainly by the fact that the excitation light incident from the surface of the panel spreads due to scattering in the stimulable phosphor plate.

The inventors of the present invention have conducted extensive studies for the purpose of improving the deterioration of sharpness due to the spread of the excitation light, and as a result, among the factors of the spread of the excitation light, at the interface between the support and the phosphor layer. Is 100μ due to the reflection of excitation light
A transparent support having a thickness of m or more is used, and a stimulable phosphor layer is sandwiched between the supports (hereinafter, also simply referred to as a phosphor layer).
It has been found that it can be effectively prevented by providing an excitation light absorption layer on the surface opposite to. In particular,
In the constitution defined by the present invention, the coloring agent of the excitation light absorbing layer is not limited to the blue coloring agent, and a more effective black coloring agent can be used.

Although it is not clear about the effect of reducing the reflection at the interface between the phosphor and the support by making the support transparent, which is the constitution defined by the present invention, it is likely that the light transmittance of the support is increased. It is speculated that this is because the reflection on the support is reduced in proportion to the amount. The transmitted excitation light is also absorbed after passing through a thick support having a thickness of 100 μm or more. Further, even if the excitation light is reflected at the interface between the support and the excitation light absorption layer,
It is speculated that this is the result of being reflected far away from the region that adversely affects the sharpness because it returns to the phosphor layer side through the thick support.

By providing a low refractive index layer between the support and the excitation light absorption layer, all the excitation light from the phosphor side reaches the excitation light absorption layer via the low refractive index layer due to the difference in refractive index. However, most of the reflected light at the interface of the excitation light absorption layer is reflected at the interface between the low refractive index layer and the support and does not reach the phosphor layer again, so the effect of the present invention is more effective. Can be increased.

Further, by setting the haze of the support to 20% or more, the return excitation light transmitted from the low refractive index layer to the support can be diffused over a wider range to a further distance, so that the sharpness can be improved. It was possible to suppress the effect on the.

The transparent support referred to in the present invention has a transmittance of excitation light of 50% or more, and preferably a transmittance of 80% or more in order to enhance the effect of the present invention.

Each component of the radiation image conversion panel of the present invention will be described below. The radiation image conversion panel of the present invention is, in the invention according to claim 1, a stimulable phosphor sheet having a support and a stimulable phosphor layer, and a surface of the stimulable phosphor layer sandwiching the support. The main feature is that an excitation light absorption layer is provided on the opposite surface. However, in the invention according to claim 2, a low refractive index layer may be provided between the support and the excitation light absorption layer. In a preferred embodiment, in the invention according to claim 4, the entire surface of the phosphor sheet is covered with a moisture-proof protective film, and the support of the moisture-proof protective film contains a coloring agent that absorbs excitation light. Or has an excitation light absorption layer.

(Stimulable Phosphor Layer) The stimulable phosphor layer is mainly composed of stimulable phosphor particles and a polymer resin, and is formed by coating on a support using a coater.

As the stimulable phosphor that can be used in the present invention, a phosphor that exhibits stimulated emission in the wavelength range of 300 to 500 nm by excitation light having a wavelength in the range of 400 to 900 nm is generally used. To be done.

Examples of phosphors that can be preferably used in the radiation image conversion panel of the present invention will be given below, but the present invention is not limited thereto.

(1) (Ba _1-X , M (II) _X ) FX: yA described in JP-A-55-12145 (wherein
M (II) is at least one of Mg, Ca, Sr, Zn and Cd, X is at least one of Cl, Br and I, A is Eu, Tb, Ce, Tm, Dy, P
At least one of r, Ho, Nd, Yb, and Er, and 0 ≦ x ≦ 0.6, y is 0 ≦ y ≦ 0.
2) The rare earth element-activated alkaline earth metal fluorohalide phosphor represented by the composition formula; The phosphor may further contain the following additives.

A) X ', BeX ", M (III) X'" ₃ , described in JP-A-56-74175, wherein
X ′, X ″, and X ′ ″ are at least one of Cl, Br, and I, respectively, and M (III) is a trivalent metal. B) Be described in JP-A-55-160078.
O, MgO, CaO, SrO, BaO, ZnO, Al ₂
O ₃ , Y ₂ O ₃ , La ₂ O ₃ , In ₂ O ₃ , SiO ₂ , Ti
O ₂ , ZrO ₂ , GeO ₂ , SnO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅
And metal oxides such as ThO ₂ c) Z described in JP-A-56-116777
r, Sc d) Be described in JP-A-57-23673, As) described in JP-A-57-23675,
Sif) M. described in JP-A-58-206678
L, in the formula, M is at least one alkali metal selected from the group consisting of Li, Na, K, Rb, and Cs, and L is Sc, Y, La, Ce, Pr, Nd, Pm, S.
m, Gd, Tb, Dy, Ho, Er, Tm, Yb, L
g) at least one trivalent metal selected from the group consisting of u, Al, Ga, In, and Tl) A fired product of a tetrafluoroboric acid compound described in JP-A-59-27980; 59-2728
Calcinated products of monovalent or divalent metal salts of hexafluorosilicic acid, hexafluorotitanic acid and hexafluorozirconic acid described in JP-A No. 59-56.
NaX 'described in Japanese Patent No. 479, wherein X'is C
at least one of l, Br and I h) V and C described in JP-A-59-56480
Transition metals such as r, Mn, Fe, Co and Ni; M (I) X 'described in JP-A-59-75200.
M '(II) X " ₂ , M (III) X'" ₃ , A, in the formula, M
(I) is at least one alkali metal selected from the group consisting of Li, Na, K, Rb, and Cs,
M '(II) represents at least one divalent metal selected from the group consisting of Be and Mg, and M (III) represents Al, G
at least one trivalent metal selected from the group consisting of a, In, and Tl, A is a metal oxide,
X ', X "and X'" are each at least one halogen selected from the group consisting of F, Cl, Br and I i) M described in JP-A-60-101173
(I) X ′, wherein M (I) is at least one alkali metal selected from the group consisting of Rb and Cs,
X'is at least one halogen selected from the group consisting of F, Cl, Br and I. j) M (I) described in JP-A No. 61-23679.
I) ′ X ′ ₂ · M (II) ′ X ″ ₂ , where M (II) ′ is B
at least one alkaline earth metal selected from the group consisting of a, Sr and Ca; X ′ and X ″ are at least one halogen selected from the group consisting of Cl, Br and I, and X ′. ≠ X ″;
Further, LnX ″ ₃ described in JP-A-61-264084, in which Ln is Sc, Y, La, Ce,
Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, E
at least one rare earth element selected from the group consisting of r, Tm, Yb and Lu; X ″ is F, Cl, Br
And at least one halogen selected from the group consisting of I and I.

(2) M (II) X ₂ · aM (II) X ′ ₂ : xEu ^{2+ described in} JP-A-60-84381 (wherein M (II) is Ba, Sr and Ca) Is at least one alkaline earth metal selected from the group consisting of; X and X'are at least one halogen selected from the group consisting of Cl, Br and I, and X ≠ X '; and a Is 0.1 ≦ a ≦ 10.0, x is 0 <x ≦
0.2) The divalent europium-activated alkaline earth metal halide phosphor represented by the composition formula; and the phosphor may contain the following additives.

A) M (I) X 'described in JP-A-60-166379, wherein M (I) is Rb and C.
at least one alkali metal selected from the group consisting of s; X'is at least one halogen selected from the group consisting of F, Cl, Br and I. b) Described in JP-A-60-221483. K
X ″, MgX ″ ″ ₂ , M (III) X ″ ″ ₃ , where M (II
I) is at least one trivalent metal selected from the group consisting of Sc, Y, La, Gd and Lu; X ″,
X ′ ″ and X ″ ″ are all F, Cl, Br and I
At least one halogen selected from the group consisting of c) B described in JP-A-60-228592,
Si described in JP-A-60-228593
O _2, P ₂ O ₅ oxide such, LiX listed in JP 61-120882 ", NaX", in the formulas, X "at least selected from the group consisting of F, Cl, Br and I D) a kind of halogen Si described in JP-A-61-120883
O: Sn described in JP-A-61-120885
X ″ ₂ , where X ″ is at least one halogen selected from the group consisting of F, Cl, Br and I. e) Cs described in JP-A-61-235486
X ″, SnX ″ ″ ₂ , where X ″ and X ′ ″ are at least one halogen selected from the group consisting of F, Cl, Br and I; and JP-A-61-23.
CsX ″, Ln ³⁺ , in the formula:
X ″ is at least one halogen selected from the group consisting of F, Cl, Br and I; Ln is Sc, Y, C
e, Pr, Nd, Sm, Gd, Tb, Dy, Ho, E
It is at least one rare earth element selected from the group consisting of r, Tm, Yb and Lu.

(3) LnOX: xA described in JP-A-55-12144 (wherein Ln is La, Y, G
at least one of d and Lu; X is Cl, B
at least one of r and I; A is Ce and T
At least one of b; x is 0 <x <0.1) A rare earth element-activated rare earth oxyhalide phosphor represented by a composition formula.

(4) M (II) OX: xCe described in JP-A-58-69281 (wherein M (II) is P
r, Nd, Pm, Sm, Eu, Tb, Dy, Ho, E
at least one metal oxide selected from the group consisting of r, Tm, Yb, and Bi; X is at least one of Cl, Br, and I; x is 0 <x <0.1
Is a cerium-activated trivalent metal oxyhalide phosphor.

(5) M (I) X: xBi described in JP-A-62-25189 (wherein M (I) is at least one alkali metal selected from the group consisting of Rb and Cs). X is at least one halogen selected from the group consisting of Cl, Br and I; and x is a numerical value in the range of 0 <x ≦ 0.2). Metal halide phosphor.

(6) M (II) ₅ (PO ₄ ) ₃ X: xEu ²⁺ described in JP-A-60-141783 (wherein
M (II) is at least one alkaline earth metal selected from the group consisting of Ca, Sr and Ba; X is F,
A divalent europium-activated alkaline earth metal haloline represented by the composition formula: at least one halogen selected from the group consisting of Cl, Br and I; x is a numerical value in the range of 0 <x ≦ 0.2. Phosphate phosphor.

(7) M (II) ₂ BO ₃ X: xEu ²⁺ described in JP-A-60-157099 (where M (I
I) is at least one alkaline earth metal selected from the group consisting of Ca, Sr and Ba; X is Cl, B
a divalent europium-activated alkaline earth metal haloborate represented by the composition formula: at least one halogen selected from the group consisting of r and I; x is a numerical value in the range of 0 <x ≦ 0.2. Phosphor.

(8) M (II) ₂ (PO ₄ ) ₃ X: xEu ²⁺ described in JP-A-60-157100 (wherein
M (II) is at least one alkaline earth metal selected from the group consisting of Ca, Sr and Ba; X is C
a divalent europium-activated alkaline earth metal haloline represented by the composition formula: at least one halogen selected from the group consisting of 1, Br and I; x is a numerical value in the range of 0 <x ≦ 0.2. Phosphate phosphor.

(9) M (II) HX: xEu ²⁺ described in JP-A-60-217354 (wherein M (II) is at least one selected from the group consisting of Ca, Sr and Ba) Alkaline earth metal; X is at least one halogen selected from the group consisting of Cl, Br and I; x is a numerical value in the range of 0 <x ≦ 0.2) Divalent europium activated alkaline earth metal hydrohalide phosphor.

(10) LnX ₃ .aLn'X ' ₃ : xCe ³⁺ described in JP-A-61-21173 (wherein Ln and Ln' are respectively Y, La, Gd and Lu). At least one rare earth element selected from the group; X and X'each being at least one halogen selected from the group consisting of F, Cl, Br and I, and X ≠ X '; and a is 0.1 <a
A numerical value in the range of ≦ 10.0, and x is a numerical value in the range of 0 <x ≦ 0.2).

[0042] (11) LnX ₃ · aM that are described in ^{JP-A-61-21182 (I) X'3: xCe 3+} ,
(In the formula, Ln is at least one rare earth element selected from the group consisting of Y, La, Gd, and Lu; M
(I) is at least one alkali metal selected from the group consisting of Li, Na, K, Cs and Rb; X and X ′ are at least one halogen selected from the group consisting of Cl, Br and I, respectively. And a is a numerical value in the range of 0 <a ≦ 10.0, and x is 0 <x ≦
A cerium-activated rare-earth composite halide-based phosphor represented by a composition formula of 0.2).

(12) LnPO ₄ .aLnX ₃ : xCe ³⁺ , described in JP-A-6140390 (wherein
Ln is at least one rare earth element selected from the group consisting of Y, La, Gd and Lu; X is F, Cl,
At least one halogen selected from the group consisting of Br and I; and a is a numerical value in the range of 0.1 ≦ a ≦ 10.0 and x is a numerical value in the range of 0 <x ≦ 0.2. ) A cerium-activated rare earth halophosphate phosphor represented by the composition formula (1).

(13) CsX: aRbX ': xEu ²⁺ described in JP-A-61-2336888,
(Wherein X and X ′ are at least one halogen selected from the group consisting of Cl, Br and I respectively; and a is a numerical value in the range of 0 <a ≦ 10.0,
x is a numerical value in the range of 0 <x ≦ 0.2), which is a divalent europium-activated cesium rubidium halide phosphor represented by the composition formula.

(14) M (II) X ₂ .aM (I) X ': xE described in JP-A-61-236890.
u ²⁺ , where M (II) is at least one alkaline earth metal selected from the group consisting of Ba, Sr and Ca; M (I) is selected from the group consisting of Li, Rb and Cs At least one alkali metal; X and X ′ are each at least one halogen selected from the group consisting of Cl, Br and I; and a is a numerical value in the range of 0.1 ≦ a ≦ 20.0. , X is 0 <x
A divalent europium-activated composite halide phosphor represented by the composition formula: ≦ 0.2).

Of the above stimulable phosphors, it is preferable that the stimulable phosphor particles contain iodine, for example, a divalent europium-activated alkaline earth metal fluoride halide system containing iodine. Phosphor, divalent europium activated alkaline earth metal halide phosphor containing iodine, rare earth element activated rare earth oxyhalide phosphor containing iodine, and bismuth activated alkali metal halide phosphor containing iodine Is preferable because it exhibits high-intensity stimulated emission, and among them, from the viewpoint of exhibiting high-intensity stimulated emission, a divalent europium-activated alkaline earth metal fluoride halide-based phosphor (Eu-activated BaFI) containing iodine is preferable. Are particularly preferably used.

From the viewpoint of light transmittance, the support used in the radiation image conversion panel of the present invention may be selected from various polymeric materials and glasses, as long as the light transmittance at the excitation light wavelength is 50% or more. However, in the invention according to claim 3, it is preferable that the light transmittance at the excitation light wavelength is 80% or more.

(Support) As a support that can be used in the present invention, a support that can be processed into a flexible sheet or web is suitable in terms of handling as an information recording material. From this point of view, For example, a plastic film such as a cellulose acetate film, a polyester film, a polyethylene terephthalate film, a polyamide film, a polyimide film, a triacetate film, a polycarbonate film, or a laminated film thereof is preferable.

In the support according to the present invention, the haze ratio is preferably 20% or more, more preferably 2
0 to 60%, and the transmittance at the excitation light wavelength is 8
It is preferably 0% or more, more preferably 80 to
It is 99%.

The film thickness of the support according to the present invention is 100.
If it is at least μm, the effect of the present invention can be obtained, but from the viewpoint of easy handling, it is preferably 100 to 500 μm.

The surface of these supports may be a smooth surface, or may be a matte surface for the purpose of improving the adhesion to the undercoat layer or the stimulable phosphor layer.

Further, these supports may be provided with an undercoat layer on the surface on which the stimulable phosphor layer is provided for the purpose of improving the adhesiveness with the stimulable phosphor layer.

(Binder) In the present invention, examples of the binder used in the stimulable phosphor layer or the subbing layer include proteins such as gelatin, polysaccharides such as dextran, and natural agents such as gum arabic. Polymer substances; and polyvinyl butyral, polyvinyl acetate, nitrocellulose, ethyl cellulose, vinylidene chloride / vinyl chloride copolymer, polyalkyl (meth) acrylate,
Examples thereof include binders represented by synthetic polymer substances such as vinyl chloride / vinyl acetate copolymer, polyurethane, cellulose acetate butyrate, polyvinyl alcohol, and linear polyester.

Particularly preferred among the above binders are nitrocellulose, linear polyesters, polyalkyl (meth) acrylates, mixtures of nitrocellulose and linear polyesters, mixtures of nitrocellulose and polyalkyl (meth) acrylates. And a mixture of polyurethane and polyvinyl butyral. Note that these binders may be crosslinked with a crosslinking agent.

(Coating of stimulable phosphor layer) The stimulable phosphor layer can be formed on the undercoat layer according to the method described below, for example.

First, a suitable solvent is added to the stimulable phosphor particles and the binder, and these are thoroughly mixed to prepare a coating solution in which the phosphor particles are uniformly dispersed in the binder solution.

Generally, the binder is used in an amount of 0.01 to 1 part by mass with respect to 1 part by mass of the stimulable phosphor. However, from the viewpoint of the sensitivity and sharpness of the obtained radiation image conversion panel, the amount of the binder is preferably small, and the range of 0.03 to 0.2 parts by mass is more preferable from the viewpoint of easy coating.

The solvent used for preparing the coating liquid for the stimulable phosphor layer is, for example, a lower alcohol such as methanol, ethanol, isopropanol or n-butanol,
Acetone, methyl ethyl ketone, methyl isobutyl ketone, ketones such as cyclohexanone, esters of lower fatty acids and lower alcohols such as methyl acetate, ethyl acetate, n-butyl acetate, dioxane, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether, etc., Examples thereof include aromatic compounds such as triol and xylol, halogenated hydrocarbons such as methylene chloride and ethylene chloride, and mixtures thereof.

The coating liquid contains a dispersant for improving the dispersibility of the phosphor in the coating liquid, and a binder between the binder and the phosphor in the stimulable phosphor layer after formation. Various additives such as a plasticizer for improving the binding strength may be mixed. Examples of dispersants used for such purpose include phthalic acid, stearic acid, caproic acid, lipophilic surfactants and the like. Examples of plasticizers include phosphoric acid esters such as triphenyl phosphate, tricresyl phosphate, diphenyl phosphate; phthalic acid esters such as diethyl phthalate and dimethoxyethyl phthalate; ethyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate, etc. Glycolic acid ester of
Examples thereof include polyesters of triethylene glycol and adipic acid, polyesters of polyethylene glycol such as polyesters of diethylene glycol and succinic acid, and aliphatic dibasic acids.

The coating solution prepared as described above is then uniformly applied to the surface of the undercoat layer to form a coating film of the coating solution. This coating operation can be performed by using an ordinary coating means such as a doctor blade, a roll coater or a knife coater.

Next, the formed coating film is gradually heated and dried to complete the coating of the stimulable phosphor layer on the undercoat layer. The coating liquid for the stimulable phosphor layer is prepared using a dispersing device such as a ball mill, a sand mill, an attritor, a three roll mill, a high speed impeller disperser, a Kady mill, and an ultrasonic disperser. The prepared coating solution is applied onto a support using a coating solution such as a doctor blade, a roll coater or a knife coater and dried to form a stimulable phosphor layer.

The film thickness of the stimulable phosphor layer of the radiation image conversion panel of the present invention is the desired characteristics of the radiation image conversion panel, the type of stimulable phosphor, and the mixture of the binder and the stimulable phosphor. Although it depends on the ratio and the like, it is preferably selected from the range of 10 μm to 1000 μm, more preferably from the range of 10 μm to 500 μm.

(Excitation light absorbing layer and moisture-proof protective film)
In the present invention, the invention according to claim 1 is characterized in that an excitation light absorbing layer is provided on the surface opposite to the stimulable phosphor layer surface with the support of the phosphor sheet interposed therebetween. In the invention according to Item 4, whether the resin layer on the support surface side of the moisture-proof protective film (hereinafter, also simply referred to as a protective film) covering the entire surface of the phosphor sheet contains a coloring agent that absorbs excitation light, Alternatively, it is characterized by having an excitation light absorption layer.

First, the excitation light absorbing layer provided on the back of the support of the phosphor sheet will be described.

The excitation light absorbing layer may be a colored resin layer formed by coating, and the resin material is made of polyester resin, polyurethane resin, acrylic resin, polyvinyl butyral resin, or epoxy resin. Is desirable.

In the excitation light absorbing layer according to the present invention, what kind of colorant is used depends on the kind of the stimulable phosphor used in the radiation image conversion panel, but as a stimulable phosphor for the radiation image conversion panel, , Usually wavelength 400
300 to 50 by excitation light in the range of ˜900 nm
A phosphor that exhibits stimulated emission in the wavelength range of 0 nm is used. Therefore, a blue to green organic or inorganic colorant is usually used as the colorant used in the excitation light absorbing layer, but in the invention according to claim 5, the colorant is preferably black. .

Colorants usable in the present invention include, for example, JP-A-47-30330 and JP-A-56-55.
No. 52, a perylene pigment described in JP-A-47-3033.
Quinacridone pigments described in JP-A-1 and the like, JP-A-47-1
Bisbenzimidazole pigments described in JP-A-8543, JP-A-47-18544, JP-A-55-98754 and JP-A-5-98754.
Aromatic polycondensed ring compounds described in JP-A Nos. 5-126254 and 55-163543, JP-B-44-16373.
No. 48-30513, JP-A-56-32165.
Azo pigments described in Japanese Patent Publication No. 50-7434,
JP-A-47-37548, JP-A-55-11715, JP-A-56-1944, JP-A-56-9752, and JP-A-56-23.
No. 52, No. 56-80050, etc., and the disazo pigments, Japanese Examined Patent Publication Nos. 44-12671 and 40-2780.
No. 52-1667, No. 46-30035, No. 4
9-17535, JP-A-49-11136, 49
-99142, 51-109841, 57-1
Examples thereof include phthalocyanine pigments described in Japanese Patent No. 48745, carbon black, and the like.

As the material for producing the protective film according to the present invention, specifically, a polyester film,
Polymethacrylate film, nitrocellulose film, cellulose acetate film, etc. can be used,
A stretched film such as a polyethylene terephthalate film or a polyethylene naphthalate film is preferable as a protective film in terms of transparency and strength, and among them, a polyethylene terephthalate film is preferably used.

The support according to the present invention preferably has a light transmittance of 80% to 95% at the excitation light wavelength, and more preferably a light transmittance, from the viewpoint of keeping the effects described in the present invention in good condition. The rate is 95% to 99%. Here, the light transmittance is calculated according to the following formula.

[0070] Light transmittance (%) = (transmitted light / incident light) × 100 The haze ratio of the support according to the present invention will be described.

From the viewpoint of improving the effects described in the present invention, particularly improving the sharpness and eliminating uneven brightness, it is necessary to adjust the haze ratio of the support to 20% or more.
It is preferably 20% to 60%, more preferably 30%.
% To 40%. The haze ratio of the support described above is A
It is measured using the method specified in STMD-1003.

The haze ratio of the support according to the present invention can be adjusted with reference to the haze ratio of the resin film used. Moreover, resin films having various haze ratios are industrially available, and the haze ratio can be adjusted by laminating these films.

In the present invention, from the viewpoint of preventing moisture deterioration of the stimulable phosphor, the protective film according to the present invention is preferably provided with moisture resistance. Specifically, the protective film has a moisture permeability. It is preferably 50 g / m ² · day or less, more preferably 10 g / m ² · day or less, and particularly preferably 1 g / m ² · day or less. The water vapor permeability of the above-mentioned protective film is JIS Z 0.
It can be measured with reference to the method defined by 208.

From the viewpoint of adjusting the moisture permeability of the protective film within the above range to improve the moisture resistance of the protective film,
It is preferable to use a polyethylene terephthalate film or a vapor-deposited film obtained by vapor-depositing a thin film of a metal oxide, silicon nitride or the like on a polyethylene terephthalate film.

In addition, the protective film according to the present invention is provided with optimum moisture resistance by stacking a plurality of resin films or vapor deposition films in which metal oxides are vapor-deposited on the resin film in accordance with the required moisture resistance. However, as a method for laminating the resin film, a conventionally known method can be applied.

In the present invention, by providing the excitation light absorbing layer described above between the laminated resin films,
The excitation light absorption layer can be protected from physical impact and chemical alteration.

From the above, the exciting light absorbing layer may be provided at a plurality of positions between the laminated resin films, or the adhesive layer for laminating may contain a coloring agent to be used as the exciting light absorbing layer. it can.

Any conventionally known method can be applied to seal the phosphor plate with the protective film, but the outermost layer of the protective film on the side in contact with the phosphor sheet is a resin having a heat-fusion property. By containing the protective film can be fused, the sealing work in the peripheral portion of the phosphor sheet can be made efficient, and the deterioration of properties due to moisture absorption of the stimulable phosphor can be very effectively prevented. .

Preferably, a protective film is arranged on the upper and lower sides of the phosphor sheet, and the upper and lower protective films are fused to each other in a region whose peripheral edge is outside the peripheral edge of the phosphor sheet. Thus, it is possible to prevent water from entering from the outer peripheral portion of the phosphor sheet. More preferably, the protective film has a layer containing the resin having the heat-fusion property described above only at the portion used for the above-mentioned sealing.

Further, when the protective film on the support surface side is a laminated moisture-proof film obtained by laminating one or more layers of aluminum film, it is possible to more reliably reduce the ingress of moisture. Further, this sealing method is easy in terms of work. Also,
In this case, it is preferable that the outermost layer of the protective film, which is in contact with the stimulable phosphor layer, is not substantially adhered to the heat-fusible resin layer and the phosphor surface.

"The moisture-proof protective film and the stimulable phosphor layer do not substantially adhere to each other" means that the stimulable phosphor layer and the protective film are not optically integrated. To do. More specifically, even if microscopically the stimulable phosphor layer and the protective film are in point contact with each other, optically and mechanically, the stimulable phosphor layer and the protective film are almost discontinuous. It means that it can be handled as a body.

In the above-mentioned sealing structure, the stimulable phosphor layer and the moisture-proof protective layer are considered to be in contact with each other at a microscopic point. This contact area is the phosphor layer area. Of 1
In the case of 0% or less, it is defined in the present invention that there is substantially no adhesion.

The heat-fusible film is a resin film that can be fused with a commonly used impulse sealer, and is, for example, ethylene vinyl acetate copolymer (EVA).
And polypropylene (PP) film, polyethylene (P
E) films and the like can be mentioned, but the present invention is not limited to these.

(Low Refractive Index Layer) In the present invention, it is preferable to provide a low refractive index layer between the support of the phosphor sheet and the protective layer on the support surface side having the excitation light absorbing layer. The low refractive index layer according to the present invention may be formed into a thin film by a coating method or a vapor deposition method between the support and the protective film, but in the present invention, a gas layer such as air, nitrogen or argon, or a vacuum layer. It is preferable to use a layer having a refractive index of substantially 1 such as a layer, which has a high effect of preventing a decrease in sharpness and is particularly preferable. The low refractive index layer according to the present invention has a thickness of 0.05
Practical use is from μm to 3 mm.

(Preparation of Radiation Image Conversion Panel) A phosphor sheet having a phosphor layer coated on a support is cut into a predetermined size. Although any general method can be used for cutting, a cosmetic cutting machine, a punching machine or the like is preferable in terms of workability and accuracy.

Although any known method can be used to seal the phosphor sheet cut into a predetermined size with the moisture-proof protective film, for example, the phosphor sheet is placed between the upper and lower moisture-proof protective films. Examples of the method include a method of heating and fusing the peripheral edge portion sandwiched between the two with an impulse sealer, and a laminating method of pressurizing and heating between two heated rollers.

In the method of heat-sealing with the impulse sealer, heat-sealing in a depressurized environment means that displacement of the phosphor sheet in the moisture-proof protective film is prevented and moisture in the atmosphere is eliminated. More preferable.

[0088]

The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.

Example 1 In order to synthesize a europium-activated barium fluoroiodide stimulable phosphor precursor, an aqueous BaI ₂ solution (3.6 mol) was used.
/ L) 2780 ml and EuI ₃ aqueous solution (0.2 mol / L)
L) 27 ml was placed in the reactor. The reaction mother liquor in this reactor was kept warm at 83 ° C. with stirring. 322 ml of an aqueous solution of ammonium fluoride (8 mol / L) was injected into the reaction mother liquor using a roller pump to form a precipitate. After completion of the injection, the heat retention and stirring were continued for 2 hours to ripen the precipitate. Next, the precipitate was separated by filtration, washed with ethanol and then vacuum dried to obtain europium-activated barium fluoroiodide crystals. In order to prevent changes in particle shape due to sintering during firing and changes in particle size distribution due to fusion between particles, 0.2% by mass of ultrafine alumina powder was added and sufficiently stirred with a mixer to crystallize. Ultrafine alumina powder was uniformly attached to the surface. This was filled in a quartz boat and fired at 850 ° C. for 2 hours in a hydrogen gas atmosphere using a tube furnace to obtain europium-activated barium fluoroiodide phosphor particles. Next, the phosphor particles were classified to obtain particles having an average particle size of 7 μm.

As the phosphor layer forming material, 427 g of the europium-activated barium fluoroiodide phosphor obtained above, 15.8 g of a polyurethane resin (Desmolac 4125 manufactured by Sumitomo Bayer Urethane Co.), and 2.0 g of a bisphenol A type epoxy resin. Methyl ethyl ketone-toluene (1:
1) It was added to the mixed solvent and dispersed by a propeller mixer to prepare a coating liquid having a viscosity of 2.5 to 4.0 Pa · s.
This coating solution was applied onto a support using a doctor blade and then dried at 100 ° C. for 15 minutes to give 270 μm.
To form a phosphor layer having a thickness of. Details of the support used above are shown in Table 1.

(Preparation of Laminated Protective Film) <Protective Film on Phosphor Layer Side> The protective film on the phosphor side of the phosphor sheet had the structure shown in (A) below.

(A) VMPET12 / VMPET12 /
PET12 / CPP30 PET: Polyethylene terephthalate CPP: Heat-fusible film (casting polypropylene) VMPET: Alumina-deposited PET (commercial product: manufactured by Toyo Metalizing Co., Ltd.) The number after each resin film is the film thickness (μm)
Indicates.

The above "/" means an adhesive layer. The dry laminating adhesive used is a two-component reactive urethane adhesive.

<Protective Film on Support Surface Side> As the protective film on the support surface side of the phosphor sheet, one having the constitution shown in Table 1 was used. In addition, the number after each layer shown in Table 1 shows each film thickness (micrometer), and "/" means an adhesive layer.

(Encapsulation of phosphor sheet) A coated sample prepared by using the support having haze and light transmittance shown in Table 1 was cut into a square of 20 cm × 20 cm, and the support surface shown in Table 1 was cut. In combination with the side protective layer, the peripheral edge was sealed by fusion with an impulse sealer under reduced pressure. FIG. 1 shows a cross-sectional view of the radiation image conversion panel of the present invention. The distance from the fused portion to the peripheral edge of the phosphor sheet is 1
Each radiation image conversion panel was manufactured by fusing so as to have a size of mm. The heater of the impulse sealer used for fusion bonding had a width of 8 mm.

<< Evaluation of Radiation Image Conversion Panel >> Using each of the radiation image conversion panels prepared above, the sharpness was evaluated according to the following method.

(Evaluation of Sharpness) Regarding the sharpness, a modulation transfer function (MTF) was obtained and evaluated.

After sticking a CTF chart on each radiation image conversion panel, and irradiating with 80 mVp of X-ray for 10 mR (distance to subject: 1.5 m), a semiconductor laser light (from the surface side having the phosphor layer A ( It was obtained by irradiating 690 nm with a power of 40 mW on the panel) and scanning the CTF chart with a semiconductor laser beam having a diameter of 100 μmφ. The values shown in Table 1 are obtained as relative values for each panel, with the MTF value of Comparative Example 1 at 0.5 lp / mm being 100.

Table 1 shows the results obtained as described above.

[0100]

[Table 1]

As is clear from Table 1, the radiation image conversion panel having the constitution of the present invention is superior in sharpness to the comparative example.

[0102]

According to the present invention, it is possible to provide a radiation image conversion panel which gives an image having excellent sharpness and a method for producing the same.

[Brief description of drawings]

FIG. 1 is a sectional view of a radiation image conversion panel of the present invention.

[Explanation of symbols]

11 phosphor 12 Support 13 Laminated protective film 14 Aluminum laminated film

Claims (6)

[Claims] 1. A radiation image conversion panel comprising a stimulable phosphor sheet having at least a support and a stimulable phosphor layer, wherein the support is a transparent support having a thickness of 100 μm or more, and the support. A radiation image conversion panel having an excitation light absorption layer on the surface opposite to the surface of the stimulable phosphor layer with the body sandwiched therebetween. 2. The radiation image conversion panel according to claim 1, further comprising a low refractive index layer between the support and the excitation light absorption layer. 3. The radiation image conversion panel according to claim 1, wherein the support has a haze ratio of 20% or more and a transmittance at an excitation light wavelength of 80% or more. 4. A phosphor sheet having a stimulable phosphor layer on a support, and a phosphor sheet disposed above and below the phosphor sheet, which is not substantially adhered to the stimulable phosphor layer and has a peripheral edge. In a radiation image conversion panel, which is outside the periphery of the phosphor sheet and is provided with a moisture-proof protective film provided so as to cover the entire surface of the phosphor sheet, the support of the phosphor sheet is at an excitation light wavelength. The transmittance is 80% or more, and the resin layer of the moisture-proof protective film on the support surface side contains a coloring agent that absorbs excitation light, or has an excitation light absorption layer. Radiation image conversion panel. 5. The radiation image conversion panel according to claim 1, wherein the excitation light absorption layer is black. 6. A method of manufacturing a radiation image conversion panel, which comprises manufacturing the radiation image conversion panel according to claim 1.